Roadside Breath Testing

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Many drivers arrested for DUI / DWI in California take a roadside breath test to determine blood alcohol content (BAC) before being arrested. Although police and prosecutors believe PAS (Preliminary Alcohol Screening) test results are damning evidence in drunk driving cases, these results can often be successfully challenged in court. An experienced California criminal defense attorney who specializes in DUI / DUI cases has the skills needed to effectively challenge PAS tests in driving under the influence cases.

DUI / DWI criminal defense attorneys have been dealing with the problems that arise with roadside breath testing for years. In the early days of roadside breath testing, it was accepted that the technology was somewhat inferior, and that roadside PAS tests were not reliable enough to be admitted into evidence. Therefore, if police used an alcohol screening test during a drinking and driving investigation, the only thing that could be introduced in evidence at a DUI / DWI trial was that the PAS machine indicated the presence of alcohol – the numeric results were excluded.

Unfortunately, that is no longer true. Courts hearing DUI / DWI cases now allow the numeric results of the PAS tests to be considered by the jury if certain evidentiary foundations are established. Therefore, motorists are taking roadside breath tests after being advised that their participation is entirely voluntary, only to have the numeric results introduced at trial.

There are two types of roadside breath tests – PAS or PBT tests, which are merely screening tests given to support the officer’s decision to make an arrest, and roadside evidential tests. There are critical distinctions between the two.

The PAS, or preliminary alcohol screening, is a voluntary test. It is not an “implied consent” test, which means that the driver is under no obligation to take a PAS test. In fact, in many states, the officer must advise the driver that the test is not required, but if an arrest is made, the driver will then be required to submit to a test of his or her blood or breath to determine alcohol content.

Unfortunately, many police officers ignore this responsibility during drunk driving roadside investigations. Many times, the driver is told that he or she must submit to a test as a collection tube is thrust into the mouth of the awestruck motorist. A DUI / DWI arrest invariably follows. It likely would have followed anyway, except now the unwitting motorist has provided additional evidence for the government to use against him or her.

The recent addition of the evidential PAS test, also known as the “E-PAS” or AlcoSensor IV XL, has made roadside DUI / DWI investigations even more complicated. These versions of the roadside breath test are the evidential test that is required under the Implied Consent Law. The exact same machine is used to administer this mandatory test as is used for what was, moments earlier before the driver was arrested, an optional test. The only difference is that they are able to print out the results instead of merely viewing the results on an LED readout.

Unfortunately, accused drivers are often unable to pinpoint the moment that they are placed under arrest for drinking and driving. One minute they are offered a roadside test, and told it is optional. A moment later, they are told that a roadside breath alcohol test on the same machine is mandatory. It isn’t hard to understand how a driver can become confused. This is why many DUI / DWI criminal defense lawyers advise people to refuse all roadside breath tests and insist upon a blood test if they are ever the target of a drunk driving investigation.

Once an arrest is made, California’s Implied Consent Law is triggered. A failure to give a blood or breath sample following a drunk driving arrest can result in administrative sanctions from the Department of Motor Vehicles (DMV) which begin with a one-year driver’s license suspension, with no opportunity for a restricted or provisional license during that year.

Roadside breath testing arose to address a significant issue in drunk driving prosecutions – because of the typical time-lapse between driving and testing, there was often an issue of whether the driver’s BAC could have been below the legal limit at the time of driving. The aim of roadside breath testing in drunk driving cases was to eliminate that issue by fixing the blood or breath alcohol level (BAC) at a time closer to the time of driving.

While this may have been a worthy goal, there are significant problems that overshadow any advances made. The challenges to both the PAS test – the pre-arrest roadside breath test – and the E-PAS – the post-arrest roadside breath test – are the same, because they are taken on the same machine. The distinction is that the E-PAS is hooked up to a printer, providing the DUI / DWI arrestee a copy of the printout of the faulty device.

The inherent flaws in breath testing work to the advantage of the accused drunk driver. DUI / DWI prosecutions are just like any other criminal case – in order for prosecutors to get a conviction, they must prove each element of their case beyond a reasonable doubt. If the prosecutor is unable to present a case that is 100 percent free of reasonable doubt, the driver cannot be convicted. This is the requirement in every criminal case, whether it is driving under the influence of alcohol, DUI drugs, vehicular manslaughter, robbery, murder, or any other offense.

In order for a breath test to prove a motorist’s guilt beyond a reasonable doubt, there are certain evidentiary foundations that must be observed. Thus, the most basic challenge to breath tests lies in the calibration, maintenance and accuracy of the testing machine. Both field breath testing units and stationhouse breath testing units are subject to problems, and it is vital to explore these issues in every drunk driving prosecution.

It’s also critical to determine whether the officer who gave the breath test was qualified to do so. There are rules and regulations regarding the administration of breath tests, and it is imperative that only those with the appropriate training perform these tests on motorists suspected of driving under the influence of alcohol.

One effective challenge to roadside breath tests relates to the technology of the machine itself. The roadside PAS devices are “fuel cell” machines. Alcohol is oxidized on an electromagnetic plate, and the amount of electrochemical energy generated is converted to a number that is supposedly equal to the blood-alcohol level of the motorist.

This technology creates the possibility that other compounds in the human breath are being misinterpreted as alcohol, and delivering inflated BAC results. Mouth alcohol is one factor that can skew the results of a breath test.

Mouth alcohol is one of the most significant problems with forensic breath testing. The danger of mouth alcohol contamination instigates many of the rules and regulations in breath testing, such as a 15- or 20-minute waiting period, observing the subject to ensure they do not regurgitate or introduce foreign material in the mouth, and the requirement of obtaining two similar results. These are all critical issues in DUI / DWI cases, and especially in cases involving the PAS machine.

PAS machines don’t have mouth alcohol detectors, also called slope detectors. A slope detector is a computer software program that is designed to detect a rapid drop-off – or slope – in the alcohol level of an individual’s breath sample. The machine is not smart enough to know whether it is analyzing alcohol molecules in the deep lung air – which is supposed to be measuring – or alcohol molecules that have been trapped in the mouth or regurgitated from the stomach. This is particularly problematic when the driver is given a breath test shortly after drinking, while alcohol is still in the stomach, or has been trapped in the mouth due to dental work, food traps, or other factors.

PAS tests also lack the ability to measure breath temperature. Every calculation the machine makes is based on the assumption that the subject’s breath temperature is 34 degrees centigrade. Unfortunately, just like the other assumptions that are made about the so-called “average” person, any variation from “average” can greatly impact the reading. Every degree of temperature elevation – which could be from illness or activities like dancing or sports – equals a 7 percent increase in alcohol percentage.

Many motorists targeted for drunk driving investigations are simply improper subjects for breath testing. DUI / DWI criminal defense lawyers are aware that those who have had recent dental work, or who suffer from GERD (gastroesophageal reflux disorder, the medical term for a type of persistent heartburn) are inappropriate subjects for breath testing. There are many other conditions that could cause an unnaturally high reading on a breath test.

Because of the inherent problems with breath testing, anyone arrested for DUI / DWI should contact an experienced California criminal defense attorney who is well-versed in these issues. The results of the roadside breath test are often the most damning evidence offered in a DUI / DWI case. It is essential that these results be challenged to achieve a successful result.

Brianna Wilkins
Brianna Wilkins